Indexing device



` A. BLAIN .INDEXING DEVICE Feb. 14, 1939.

Filed Feb. 5, 1958 3 nnento`r O Mw G ttorneg Patented F eb. 14, 19139 f UNITED STATES PATENT OFFICE INDEXING DEVICE Albert Blain, Philadelphia, Pa., assigner to Radio Corporation of America, a corporationof yDel- Application February s, 193s, serial No. 188,947 5 claims. (ci. 11a-124.2)y

This invention relates to indexing devices such, for example, as may be employed in radio or television apparatus for adjusting and for indicating the angular adjustment of a tuning control or other shaft.

An object of the` invention is to provide an indexing mechanism capable of being rapidly and accurately adjusted.

Another 'object of the invention is to provide a simple and inexpensive indexing device and one without gears whereby back lash and other objectionable features of the prior art are substantially'obviated.

Another object of Vthe'invention is to Vprovide an improveddual-ratio driving mechanism capable of being adjusted with micrometer accuracy.

Other objects and advantages, together with certain details of construction, will be apparent and the invention itself will bebest understood by reference to the following specification and to the accompanying drawing, wherein Figure 1 is a, front elevational view of an indexing device constructed in accordance with the principle of the invention, and A Figure 2 is a side elevation, partly in section, of the device of Fig. 1.

In the drawing, I designates the base of a radio chassis and 2 aV U-shape bracket supported on said base. Immovably supported on bracket 2 is an index plate 3 and a bushing 4 through which extends a rotatable tuning control or other driven shaft 5. Shaft 5 is provided with an extension 5a, upon which a driving shaft in the form of a sleeve 6 is mounted for rotation. VThe driving shaft or sleeve 6 has a driving element, exemplied by a knob 1 secured to its outer end, and intermediate' its ends has a fixed hub' secured thereto as by set screws 9. Also secured on the hub 8 for rotation with the driving shaft 6 is a dial I0 and behind this dial is a second dial I I Y which is supported for relative movement with respect to lthe first dial; that is to say, the second dial II may be moved in a manner later described about the ixed hub 8 on the-rotatable 6` when the knob 'I is turned. As clearly shown in Fig. 1, the camV selected for purposes of illustration has a rise of substantially 360 and is provided with a stop I4 which extends radially outward at the terminals of the rise.

Secured directly to the driven or main shaft 5 in the space intermediate the cam I3 and the forward face of the fixed index plate 3 is an outwardly extending arm or plate I5 which may be bent forwardly and then outwardly, as shown at I5a, Fig. 2, to present its central peripheral portion |511 (Fig. 1) in a plane parallel to its main surface. An arcuate slot |50 is preferably provided in the bend of the plate I5. I

Plate I 5 serves as a support for an L-shape link member I6 which is pivoted thereon at a point remote from the shaft by a pivot I1 (Fig. 1) located in the elbow of the L. One of the arms I6a of the L-shape member I 5`extends through the slot I5c and is provided with a terminal portion I 6by which extends rearwardly above and adjacent theperiphery of the immovable index plate 3. Part Ib of the L arm constitutes a retaining Vmember for a ball I8 which is adapted to be selectively seated in any of a plurality of complementary detents 3a. which are arranged in spaced relation on the periphery of the index plate 3. To provide a spring force for maintaining the ball in a selected detent, the ball retainer is provided with a loop portion I 6c at the radial end of the L-arm I6a.

The other arm of the pivoted L is designated Id; it is provided at its outer extremity with a cam follower I9 whichis adapted to be maintained against the edge of cam I 3- by a spring 20 which is anchored at one end to the plate I5 and bowed about the pivot I1 so that its opposite end exerts a. biasing force against the arm Ilia which is transmitted through the L to the cam follower.

It is now apparent that the ball I8, when it is seated in a detent 3a, constitutes an axis of rotation for the L-shape link member I6. Thus, any force applied through the cam follower I9 to the arm I6d of the L and tending to raise or lower the said arm will be converted into a rotary force which will be applied to the plate I5 through the pivot I1 which connects the L tothe plate. Since plate I5 is fixed on the main shaft 5, the rotary force applied to this plate by the rise and fall or toggle movement of the L will drive that shaft. The toggle in this case may be considered to comprise (1) that portion of plate I5 which extends from the axis of the driven shaft 5 to the'pivot I'l and (2) that portion of the L-shape link member I6 which extends from the ball I8 to the pivot I1.

The force required to produce the above described toggle movement of the L-shape member is applied thereto through the cam follower I9 as it follows the rise of the rotating cam I3.

In Fig. 1, the cam follower I9 is shown against that surface of the cam stop I4 whereat the rise of the cam (as measured from-the axis of the driving shaft) is shortest. Therefore, when the cam I3 is moved in a clockwise direction, the cam follower I9, in following the rise of the cam, will urge the arm Idof the L upwardly :thereby pivoting the L in a counter-clockwise direction about the ball I8, which, being-ina detent,serves as an axis or center of rotation'of the L. Now,

since the L is xed to the plate I5 by the pivot I'I, the above described counter-.clockwise movement of the L about its center of rotation (i. e. ball I8) will cause the plate and hencethe driven shaftj5 .(to which plate I5 is fixed) tobe driven in the lsaine (clockwise) `direction as the driving shaft 56 and the `cam I3 thereon are being driven. 1 n

Obviously, the angular distance that the main shaftr will be -driven when the cam I3 is rotated V360" (i. e. Vto that position'whereat the cam stop 14 is to the left of the-cam follower I9) .is .a function of the radial vdistance the cam follower must Vtravel in moving from one side of the cam stop'to the other side, around the cam. If this distance or rise is small (as it is Vin the illustrated vembodiment of the invention), then the step-down ratio lbetween the driving and driven shafts will be relatively enormous, so that I the cam stop` I4 against Vthe cam 'follower ISl detent on the main (rear) dial scale II.

^ force is positively applied.

in units and vfractions of units of 10.

will unseat the ball I8 (the spring action of its retainer permitting this) .and drive the plate yI5 and hence the drivenshaft y5 asvlong as :such Thus, the driven shaft may be said to :be directly coupled to the driving shaft as long' Aas Vthe cam follower I9 is in contact with one side or the other of the cam stop I4.

As `previously pointed out, the inner or larger, dial II is mounted to permit of its being rotated with respect 'to theouter, smaller,` dial I0. Such movement is imparted to the inner-dial II by the cam follower I9 which extends through a slot-l ILL-provided for the purpose in the said-dial. This slot IIa is made somewhatlarger thanthe cam follower I9 so that no movementis imparted to the dial II by thepreviouslydescribed rise and fall of the Larm [5d to which the .cam follower is aixed.

There are thirty-six detents `3a in the index plate 3 ofthe illustratedY embodiment ofthe 4invention and there is a mark individual to each Thus, the main scale indicia'represent 10 increments indicative of the angular position (with respect to the pointer I2) `ofthe maintuning shaft`5. The secondary (front) scale IIlmaybe calibrated This front scale Illk is read with reference to the zero position ofthe main scale I I, and the main scale is read with referenceto .thepointer I2. Thus, the twoscales when read together provide. a reading in degrees. andy fractions `of `a ldegree of .the

angular position of the driven shaft 5 with respect to the pointer I2.

While the invention has been described as embodied in an indexing mechanism for radio apparatus, the invention is not limited to such application as the disclosure in this respect is merely illustrative for purposes of explaining the inventive concept. The invention is therefore not tobellimited except as requiredby the prior art andthe spirit of the appended claims.

What is claimed is:

E1. In a device of the class described, a rotatable fshaft, a sleeve mounted for rotation on said shaft, a camk fixed on said sleeve, said cam having arise ythereonand a stop at the terminals of -said-riseyan arm fixed on said shaft, an L- shape link pivote'd'at its elbow to said arm at a point rremote from the axis of said shaft, a

carn follower on one arm of said L and adapted -'to follow the rise of said cam and to engage said L stopa ball .and a ball retainer on the other arm of sa-id v.L, a -xed index plate having detents thereon arranged in spaced circumferential relation with respect to theaxis of said shaft, said detents being positioned in the path of -said ball, said ball .when in a detent constituting an axis of rotation for said L when the cam follower thereon is raised or lowered by means of the cam; rotation `of said L-about the said ball-axis serving to transmit torque through its pivot to the arm'to -whichsaid yL isafxed and thence to said shaft; `andmeans for rotating said sleeve.

2. The invention as set forth in claim 1 wherein a main scale is provided, `said main scale being mounted `about the axis of rotation of said shaft .and yadaptedto be moved by the cam follower `in-dscrete steps when the axis of rotation of the r`L is `'shifted from `one detent to another by the force transferred to the cam follower through the cam stop when said stop is rotated in contact with the cam follower.

3. .The invention as set forth in claim l whereinamainscale and a secondary scale are provided, said main fscale being mounted to be driven. in .discrete steps by movement of said cam follower, and said secondary scale being mounted on said` sleeve for rotation therewith, a fixed pointer forsaid main sca-leand means on said main ,scale .constituting a .reference point for said secondary scale.

.4. In. a device of the class described, a driving shaft,.a1 driven shafta,cam on-said driving shaft, a stopvon said,cam,.means comprising a toggle connected to said drivenshaft and having a cam follower thereon biased to Yfollow said cam, and means for.changing the .direction of motion of saidftoggle -when said cam follower is moved in Contact with said cam stop, whereby to alter the driving ratiobetween said shafts.

5. `In a device ofthe class described, a driving shaft, a driven shaft, a cam onsaid driving shaft, a stop-,on\said cam, a plurality of toggle elements connected to said driven shaft and having a cam follower thereon biased to'follow the cam surface of saidacam, said cam stop, cam follower and certain of said toggle elements constituting a direct driving connection between said driving and driven-shafts, said cam surface, said cam follower and the other of said toggle elements constituting yan-indirect driving connection between said shafts,and means'for changing from indirect to direct driving relationwhen .said cam follower is movedin .contactwith said cam stop.

ALBERT BLAIN. 

